A-ZEB project progress report: Set of cost-effective NZEBs

April 2018:

Set of solutions for cost effective NZEB’s

AZEB aims to combine the knowledge and experiences of stakeholders and existing case studies into a set of solutions for the development of cost effective new NZEB’s. This set of solutions will form the basis for the AZEB methodology, that will give guidance to specific target groups in the market to create affordable (nearly) zero energy buildings. These target groups are decision makers and experts, who can use the methodology to make cost optimal decisions, give cost optimal advice and cost optimally implement the decisions made.

Cost drivers for NZEB

There is a number of cost drivers that are specific for nearly zero energy buildings. With cost driver we mean a factor that significanntly increases the lifecycle costs of a building. Within AZEB we look at cost drivers for NZEB,  compared to a traditional building. Examples are the extra costs of materials in the construction phase, the extra costs of verification and validation tests in the construction phase, the extra time needed for optimization of design due to lack of specific NZEB expertise or lack of use of calculation and simulation tools in the design phase, the cost of risks associated with workers that are unexperienced in NZEB detailling in the construction phase (more time needed, more rework due to mistakes), suboptimal designs because NZEB cost effective design principles were not followed (leading to e.g. overdimensioned building services or excess material costs).

Set of Solutions to control the cost drivers and cost optimize the building

We identify three types of solutions to cost optimize the lifecyclecosts of Nearly Zero Energy buildings.

  1. Clear performance indicators on cost, energy, comfort, health and environment.
  2. Cost optimal technical and energy concepts
  3. Methods for optimizing processes within the building value chain



The first type of solutions create the boundary conditions for controlled cost optimization efforts. There is still much unclarity in the market about how to define energy performance or on how to define and assess important user oriented performance indicators such as health and comfort. In nearly zero energy buildings, design choices, execution in the construction phase and user behaviour and maintenance in the use phase have a strong impact on the complete performance of the building. Correct execution of details is much more critical for performance than in traditional buildings. Therefore the performance targets need to be made clear and explicit to facilitate decision making for all stakeholders involved during the lifecycle of the project. A balanced set of indicators is also needed when applying any kind of performance contract in the project to control risks. In addition, when new insights during the project occur, a clear set of indicators can make sure decisions can be validated with the complete set of original purposes of the project, ensuring client satisfaction and continued performance of the building.

Cost optimal Technical and energy concepts

The second type of solutions, technical and energy concepts, will provide clear guidelines to design, build and maintain a cost effective NZEB. These solutions entail e.g. cost effective design principles (such as building orientation and shape to reduce loss of energy and gain maximum solar exposure in winter), cost effective building service concepts (such as combining several functionalities in one element) and the use of specific calculation and simulation tools for optimizing design.

Reducing costs of waste by optimizing processes

The third type of solutions focusses on eliminating wastes in all phases of the project. AZEB follows the philosophy of lean in this, identifying 8 types of waste: defects, overproduction, waiting, underutilization of talent, transportation, motion, inventory, extra-processing. The presupposition is of course that these types of waste create unnecessary costs. Within AZEB solutions are collected to reduce these types of waste for NZEB projects and for the NZEB value chain. These solutions have implications on the project scale, but also on the scale of companies and the complete value chain. Although many of these solutions are generic for all types of building projects, not just NZEB, we still integrate them in AZEB because the necessity to apply them will rise once the NZEB standard is enforced by law in Europe (2020). The challenge will then be to keep housing affordable, even with these high energy standards. AZEB presupposes this can only be done by increasing productivity and reducing waste throughout the supply chain.

Towards an AZEB decision making guideline

The AZEB methodology will integrate these three types of solutions into a step-by-step decision making guideline for decisionmakers. In addition relevant factsheets will be created, which clarify the solutions in greater detail and which direct the reader to relevant training material.

A first overview of our identified solutions until april 2018 can be found in this article:

Set of Solutions for Affordable Zero Energy Buildings: Preliminary results.


Although this overview is still rough and needs to be integrated into our AZEB methodology the coming months, we wish to already share these preliminary results for those who are interested.